Comments Off on It’s never too late to be what you might have been- A winged hammer’s tale.

From time to time we lift a story from our forum and put it here for the wider world to enjoy. This is one of those occasions. Mole is one of our winged hammers and if you ever found yourself wondering whether it was too late to take up track racing or thinking you needed mega-bucks just to get started, Mole’s story should provide some inspiration.

What started as a bit of laugh has seen Mole win his local class championship and this year, Mole will take on both Donington’s classic endurance round in May and Spa in June.

This is Mole’s story, so far…

This is how it all began. It was Christmas 2012.

I had a perfectly mental, tuned GSXR thou and I got talked into going racing. After all, I was 46 and if I didn’t do it now, I never would. My mates were racing in the Post Classic series and, if I wanted to take them on, I needed a pre ’88 bike to do it on.

I got £1200 and the horrible 750 Slabby streetfighter you see below for my pride and joy(oddly I don’t miss it).

It was standard apart from the Blandit 600 wheels, carbs and a really loud,rattly can. The weird seat unit looked ok but weighed a ton. The brakes were knackered and the motor was seized.

I had 3 months to turn it into a competitive race bike.

Not having a clue about racing didn’t help. I looked on the web at racing Slabbies and dreamed of world championships. I looked at frame mods as I had heard that the standard frames were far too flexible. I got some 6mm alloy plate and a length of 40×20 box section and made up some bracing. I don’t have the capability to alloy weld so I taped them onto the frame and took it to the local blacksmiths to get welded up. I bought an aftermarket fairing on Eblag then realised that it didn’t meet the catch tank regs so pop riveted a bit of caravan onto the bottom. I made a couple of brackets to fit R1 calipers to the Slabby forks,fitted clipons, an R1 shock, an 1100M back wheel, painted it matt black and poured diesel down the plug holes. After a couple of days it was turning over and running on a set of VM29s that I already had.

I was ready for action.

Season 1

As I said, I didn’t have a clue about racing. My mate Iain P was coaxed into helping me. He was in strong disagreement that the best way to find the limits of adhesion was to lean more and more till I fell off (both left and right). But that’s what I did. My first race was at East Fortune. I did a 1:17 and fell off. The bike felt horrible, Skittish and downright dangerous in the damp with road legal tyres as we weren’t allowed wets. Not helped by the fact I was running them at road pressures of 36 front and 42 rear. When I asked someone about it they pissed themselves laughing and told me to try 31 front and 28 rear. What a difference that made!

There were 15 riders in our class and by the end of the season I was down to a 1:08 and finished second in class.

Season 2

Second season and I had made a few changes.

I bought another fairing and took all the bodywork to my mate Wee Stuart the painter and told him to paint it the same colour as the car I was getting sprayed. The car looked better! I got dogs abuse all year about that colour. Luckily enough I crashed it at the last meeting of the year so it would need painted again. It got a Gsxr600 K1 front end with a ZX9 wheel, fireblade calipers and a shortened random, and much more sociable, end can. All much cheapness as money was tight. Best buy was the Taiwanese rear sets. £36 and made from an alloy I had, and have never since, encountered. They crash really well. When bent double they can be hammered straight again and again. I decided to go with no proper seat as comfort is the last thing on your mind when racing.

It was tight that year, but I won by a handful of points.

Season 3

Season 3 and I have a target on my back!

The team: Jools-Team principal- cook

Iain P-Crew chief- Prophet of Doom

Me- Ballast-Talent(depending on results)

The big change for this year was my mate Andy Fyffe bought me a set of PFM discs. He has the superbike ones on his Harris Magnum4 and swears by them. He’s not wrong., Combined with Bendix carbon matrix race pads, they are like hitting a skip!

I bought a second hand stainless race pipe and can, some cheap chinese levers, a kid on seat and new paint.

A proper race loom was made up and doubts were cast as to the longevity of the still original de-seized motor(as can be seen by the amount of oil on the tailpiece)

There was no way I was going to win this year after a couple of crashes(silver Gaffa tape is my new best friend)

As luck would have it, Andy Lawson who was sure to beat me, went off to do the Manx (and won his class) so that left me winning by a handful of points again this year(2014)

Season 4

First major revamp. I bought a load of Gsxr bits from someone who was moving class to supertwins. The package came with a blown 750m motor with a lightened and balanced crank and a Wiseco 771cc kit. It had dropped a valve and destroyed the head and piston but the cylinder was untouched and came with a new piston kit. Also in package was a low mileage 750m motor and a Dyna 2000 ignition set up. Because I’m a slack arse, I decided to put the complete 750m motor into the bike along with the Dyna ignition and find another head, to get ported, for the trick motor for a later , more points demanding stage in the championship. The Prophet of Doom was in total agreement, much to my surprise,but only because he doesn’t like change. A new swoopy slingshot body kit was purchased. Again only because it was £100 cheaper than a Slabby one. At least the people that make “race” fairnings reckon that you will need a full belly pan for a Slingy. Painted it myself this time. Looks fabulous from a good few feet away. Changed to 36mm CVs( forgot to mention that the year before I had the VM29s bored to 33 at the back to match the fronts). The 36s used less petrol which worried me.

I put Hyperpro springs in the forks which greatly improved the handling. Unfortunately this meant I started having ground clearance issues. I moved the pegs up and back a little, made a new link pipe for the exhaust to tuck it in and cut holes in the fairing where the bulges for the engine cases were.

Halfway through the season is when the electrical gremlins joined the team. The bike would seem fine for about 8 laps of the 10 lap races then start misfiring. We kept finding dodgy connections (caused mainly by using those shitty blue connectors). We would think it was sorted but it would do the same thing again. We changed the plugs, the coils, made another loom and even tried a better fuel tap in case it was petrol starvation. Nothing seamed to make a difference. It was at one of the spark plug changes (last race of the weekend) that a rogue (and tiny) nut had found its way down the plug tube so that when the plugs were taken out, it fell in. The motor sounded terminal on startup so the bike was put in the van. The trick motor was put into service by using the head from the standard motor. That’s when I noticed the tiny square nut embedded into the edge of the combustion chamber.

The rules were still the same regarding tyres. Road legal only. No wets. We were running Pirelli diablo supercorsas in the dry and Michelin pilot road 3 touring tyres in the wet.

I’ve ridden bikes all my life and most of it in Scotland so riding in the rain doesn’t bother me. This worked well in my favour as it was wet a lot that year. I won the championship by a fair bit and went the whole season without crashing.

Season 5

The class was beginning to dwindle with only 8 bikes left. The racing was still good though. My main rivals Gordon Murray on his VFR and Gordon Castle on a very well put together Gsxr 750 were always right with me. I was still having ground clearance issues because the bike was handling so well. The NRC casings were getting scuffed as was the fairing although I had pulled it in as much as possible. I made up brackets to move the top mount of the shock back and down which meant I had to take more meat off the linkage to allow more height. They look dodgy and I meant to get them welded onto the frame but never did and they haven’t moved. I should still get them welded on.

Deek had joined the team as pit crew and moral prevention officer. Mostly he noised up the competition.

At the Bob Mac Memorial classic races that year I did my best ever lap of 1:03.7. This was only possible because of the perfect weather conditions and having a couple of world class riders to chase. I never beat them but they dragged me along a full second faster than I had gone before.

Wet tyres were allowed! They are epic. If you have never tried them you wouldn’t believe how grippy they are. I prayed for rain and did my rain dance every meeting.

The gremlins were still on board. I was over riding the bike when it was stuttering on the last laps and ended the season with a couple of crashes. The bike was fast though and I could build up enough of a lead to still finish 1st or 2nd. I managed to win my fourth consecutive title. Just.

Season 6 2017

I had been warned not to run the number 1.

What do they know!

Over the winter I had bought another motor that had just been built by a renowned tuner. It had Wiseco high comp pistons and a ported head. Unfortunately for the guy his fuel tap had not shut off and filled the cases with petrol resulting in a big end failure. We made an engine up from all the best parts we had. It’s a total screamer. New paint and another end can and we were ready.

First race of the year and the bike died after 3 laps. When the race was over it started and ran perfectly back to the pit.

We checked everything we could think of. I was told the Dyna 2000 ignitions were bomb proof and no way it would be that. I didn’t have another one anyway.

The class was only 5 strong and we were out with the CB500s. It meant we only got 2 clear laps before we were in traffic. That worked in my favour as the bike was still playing up and I managed to finish 2 of the races.

I was convinced that it was a fuel starvation problem so for the 2nd meeting i bought new Mikuni RS34s and fitted a Pingle tap. On a sneaky test ride along the back roads the bike felt great and never missed a beat. At the meeting on the practice session the bike ran perfectly. However when the call went out for qualifying it would not start. No spark.

One of my rivals lent me his spare Dyna ignition. That was the problem all along. I had to start at the back of a 36 strong grid (30 pizza bikes and then the post classics). By lap 5 I tried to take the lead and crashed. Bugger! It had ripped all the controls off the left side of the bike. We had enough spares to sort the bike and hammered straight the unbreakable Taiwanese rear sets. 2nd race and the gear linkage snapped on lap 2 and in 5th gear. I finished the race but burnt out the clutch slipping it out of the tight corners. I didn’t have a spare clutch so I roughed up the steel plates. It was better but still slipping. 2 distant 5th place finishes.

I could still win the championship (theoretically) if I won every race.

At the 3rd meeting everything went perfectly. I won all the races and my nearest rival had a DNF. It was on.

Last meeting of the year. First race. Pole position. The lights went out and my throttle cable snapped.

Fixed the cable by soldering a new nipple on. 2nd race. 2nd lap and the cable snapped again.

It was over.

Won the last 2 races but finished a distant 2nd in the championship.

Good riddance number 1 plate.

Roll on 2018.

Mole.

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Oh no, here he goes again, twittering on about “evolution , not revolution” and “genetic engineering of an extinct species”

Well, nearly but not quite. I’m going to mix it up a bit this time and tell you a tale of evolution AND revolution.

Back in the Dino days of the old site there were many lovely bikes built but because they were scattered around the world you didn’t always get to see them in the flesh. I travelled a lot for OSS and I was lucky enough to see quite a few, close up. Some lived up to the hype and some didn’t. (I include my own creations in the latter category)

As luck would have it though, I didn’t have to travel far to see a bike, where the opposite was true. The pictures I had seen of this bike online, before I stumbled across it at a local bike meet, had not done it justice. That bike belonged to Gregg Campbell AKA Wee Man.

Looking around Gregg’s GSXR1100M Slingshot you could just tell his had been a long and intense love affair. It had the look of a bike that had been tastefully, and carefully evolved to meet its owners exacting tastes and requirements. All of which, were very tidy and meticulously well executed. If our FBOB had been there, he would have been forced to say “bugger me that’s shiny”. It instantly got my “bike you’d most like to take home” vote.

“But KM you promised us a revolution as well as an evolution!”. Easy tiger, I’ll get to that bit.

Fast forward a few years and I’m loafing around at the Fast by Me workshops drinking coffee and listening to Dave telling me about how he took an angle grinder to his modem, while on the phone to his internet provider’s customer support line. Out of the corner of my eye a familiar bike caught my attention. It was none other than Gregg’s Slingshot. “I know that bike” I said. Now we all know what happens to anything that goes to uncle Dave’s. That’s right, it gets the boost.( unless it’s a faulty modem)

The boost is pretty much Dave’s solution for everything ( I think he’s onto something). Gregg’s Slingshot was in for one of Uncle Dave’s rock solid turbo kits. Even Dave paused his internet tirade for a moment to chip in how tidy the bike was.

I’m sure Gregg will agree with me that the arrival of “the boost” has been anything but evolutionary and every bit Revolutionary! (made it, see)

This tells you all you need to know about limitless possibilities offered by 80s and 90’s Suzukis. The best part of breaking up, is making up, especially when the making up bit includes a extra-large bucket full of lairy charged up horses.

My slabby has a lively front end, so I’ve been wanting to fit a steering damper for ages. I even acquired the period Daytona fitting kit and damper however couldn’t get that to work with my USD front end. So, seeing as I wasn’t keen on modifying the frame to take a bolt-on side mounted damper the only option left was a 916-style fitment. Seeing as I’m running an Ohlins rear shock, the damper had to be Ohlins to match of course!

Basic theory:
Whilst steering damper manufacturers don’t list fitting kits for oldskool bikes, it’s actually a simple matter of taking the measurements and then doing some research to find a suitable kit (or parts from several kits).

The measurements: (Note – some measurements are taken with internal vernier edges, some external. These are just shown to illustrate, you should of course check your own measurements carefully!)

A: Yoke nut centre to tank front mount centre

B: Top of tank mount to top of top yoke

C: Between centre of tank front mount bolts

D: Between LH lock and centre (then multiplied by 2)

The research:
I took a tape measure with me to bike meets, bike shops etc to measure up more modern bikes (with owners permissions of course when they were about!) and also bothered a few people selling kits on ‘that auction site’.

Things to note: On my slabby, the damper is quite close (5-10mm) to the tank. Double, triple check all measurements to ensure it won’t foul anwwhere. Source the fitting kit before buying a damper so that you can mock up and modify if necessary. Setting a good search on ‘that auction site’ makes this surprisingly easy and cost-effective. For the damper stroke, obviously err on the side of slightly longer but not too long as it will look unbalanced.

The result: I picked up a 2000-model H*nda Firebl*de Harris fitting kit from ‘that auction site’ for a whopping �20. Measurements were near-perfect as a 1-2mm on the tank mount, etc. is just fine. Only slight drawback was 30mm lower ‘B measurement’ so I acquired a 30mm tubular spacer.

My ‘D measurement’ (remember to multiply by 2 of course!) meant an approx 60mm stroke damper so I ordered a 63mm stroke Ohlins damper from BikeStuff (cheers Rich!).
In the pics below you can see the finished result. I’ve lost a tiny amount of right-lock, however, eventually I’ll get a spacer made up to under the tank-mount part which will solve that. All-in-all I’m well pleased!

When I was studying my new 38mm slingshot carbs my eyes fell on the small rubber hose which runs along the outside of the carbs from the float chamber to somewhere above the intake. I disconnected the hose and started tracing the circuit inside the carb.I did this by reconnecting the hose to one of the fittings and bowing into it. So by hearing where the air escapes you know the routing of the circuit.

The top fitting connects to the uppermost hole in the bellmouth, but when I blew into the fitting of the float chamber I seemed to have hit a dead end because there wasn’t any air escaping. I noticed a small plug which looked like a jet inside the float chamber. I removed it and now I could blow trough it. First I thought the jet had been clogged but after closer inspection it really was a plug instead of a jet. So there was a hole in the bellmouth that connected to the float chamber, but the hole was plugged. I had some sleepless nights trying to figure out what the function of this would be.

Then I decided to do some investigation on the web. I didn’t expect to find much info on Mikuni carbs on the web, but suddenly I found this article deeply hidden inside Factory Pro’s website…

Power jet carbs – Mikuni’s great addition to a carb used in a high rpm application.

The power jet adjusts high rpm mixture, in the gsxr750 – from 10 to redline, in 1/3rd the step of a main jet change. Changing a main jet, in the 38mm carb, as installed on the gsxr750, adds or subtracts up to 2% CO per main jet change – when the CO% needs to be adjusted in in .2%-.4% for best power attainment. Changing the power jet allowed much finer increments of change and, just as critically, happened to change the fuel delivery curve to what was optimum for the gsxr750 – something that would have required main air jet changes and other modifications to attain, but would still leave the main jet fuel delivery steps too coarse. Strange. This Powerjet circuit works wonderfully when tuned on the stock airboxed gsxr750 (and it’s pretty straightforward to tune on our EC997 Low Inertia Eddy Current dynamometers unlike simple inertia dynos.

The method of operation is as follows. At full throttle, as the rpm increases, at exactly 10k, there is enough of a pressure differential between the float bowl and the airbox interior to draw fuel up the black hose on the LH side of the carb and exiting through the hole at the top of the bellmouth of the carb. The fuel is metered by a jet that is located in the bottom of the float bowl. The jets are sized in increments of 2.5 or .025mm. Usual size for a gsxr750 with a stock airbox and air filter might be between #58 to #67.5. The power jet circuit, when properly tuned, adds the equivalent of 2-3- main jet sizes “on top” of the main jet, so, if you were not using the power jet circuit, i.e. had a “0” or blanked jet installed with a #125 main jet, you would use a #117.5 with a #62.5 power jet installed.

Since this particular circuit works on the pressure difference between the float bowl and the airbox interior, it is absolutely affected by any change in the pressure differential. If the air filter is changed to less restrictive unit or the airbox inlet is modified, creating less restriction – the power jet area (size) should have to be increased above the usual size, though, a BMC or K&N, as installed for stock replacement, may only require 1-2 sizes increase in the power jet (in addition to +2-+3 on the main jet circuit).

If the airbox is removed, there is no longer a sufficient pressure differential to pull the fuel up the ~2.5″ vertical rise from the float bowl to the outlet in the bellmouth and the circuit is no longer effective.

Why is the Powerjet circuit difficult to tune on a simple inertia dyno and easy on our EC997 Low Inertia dynamometer? According to the former owner of Dynojet, the powerjet circuit simply doesn’t work because there is a lag in fuel delivery at 9.5k rpm – creating a flat spot there. It turns out that the reason that he saw that is that the dynojet dyno has insufficient load to simulate the Real World Loading ™ that is present on the bike in 4th and higher gears on the road or track. There is a slight delay in the onset of Powerjet fuel delivery, but it’s only vaguely present in second gear in the real world, and not present in higher gears due to the slower acceleration rate that occurs when you are actually riding. If you were racing, as Yoshimura USA and other non sponsored, large US Suzuki sponsored teams (we lent them carbs for the Finals) verified, the kit outperformed anything dynojet had to offer.

How to tune: 1. Install the main jet that produces the best power at full throttle / 8k-9k. 2. Install the powerjet set that produces the best power at full throttle / 10k to redline. 3. Raise or lower fuel level to get best power at full throttle / 3k. 4. Recheck main jet and needle height if you needed to lower the fuel appreciably. 5. Adjust fuel screws for best idle. Note – this is the “short” tuning list!

Benefits: The size of the main jet DOES affect the low and midrange. Excess leanness isn’t usually the problem on these carbs. Using a #117.5 vs. a #122.5 main jet (PJ equipped vs. using a #0 PJ ) leans and crispens the lowend and midrange for better off idle and corner exit performance.

There other applications on other motorcycles that use circuits that are called “power jet” circuits that work on different principles – some are electronically controlled and work in the midrange like RGV250, the RS250 for upper topend, where they activate and deactivate through different ranges and still others work for different reasons and by different principles. “Power Jet” is a catchy sounding name and it gets used every few years or so…

Why did Suzuki specify that US and UK models, for example would have a blank or “0” jet installed, disabling the circuit and other countries, like Canada, got the activated power jet circuit (though with pretty odd settings)? Emissions? I don’t think so. With the basic fuel level and needle settings virtually the same on both applications, using the larger main jet, as required with the circuit blanked, would only increase hydrocarbon emissions under measured conditions.

At any rate, the circuit works extremely well in dealing with the coarse main jet metering steps of the older style gsxr750 carbs – 1st through 5th place at the 1990 WERA Grand National Finals used our Factory Pro #CRB-S06-1.0 Carb Recalibration Kit. Pervasive kit use followed for the next couple of years -until 1992, the last year of the power jet.

Says it al really, but what I can’t figure out is why mine have size 0 jets fitted as my carbs came from the UK and so should have a functional circuit according to the article.
But anyway, as I am using separate K&N’s the powerjet circuit won’t be able to function properly so I removed the tubes and plugged the outlets inside the bellmouths.
This way you won’t have to disconnect the tube every time you want to change the main jets which can save you a lot of dyno time and therefore money. Now you only have two screws for the top cap and two for the float chamber which makes them very service friendly.

Now that we are talking carburation technology I would like to point out two other things that are important.

When I remove the airbox and fitted separate K&N’s there were a few hose fittings that I didn’t know what to do with. In the middle of the bank of carbs there’s a 14mm big hole which acts as a breather for the float chambers. You need to connect a hose to this which is about 30 centimeters long to

A.) prevent dirt from entering the float chambers, maybe you’d even fit a small filter to the other and of the hose. A good and cheap trick is to nick some of your girlfriend’s nylons, put a piece of it at the end of the hose and keep it in place with a tie-rap.
B.) create a kind of buffer for the air pressure below the diaphragms. This is very important for the same reason you need to add tubes to the fittings of the float chamber breathers.

You need to connect a tube about 20 centimeters long to the fittings of the float chamber breathers which are located between carbs 1&2 and 3&4. If you don’t do that the air pressure inside the float chambers will become very perceptive to pressure changes outside the carb like when you get some sudden sidewind or pass a big lorry.
I didn’t believe this at first until a dyno operator did a run before- and after fitting the hoses. The hoses made the powercurve much smoother and therefore made it easier to choose the right jetting.

In the US, with a stock airbox, we didn’t have ANY problems with crosswinds, even 40-50mph gusting crosswinds at full lean at 100mph boogie. Actually, there is one problem – getting broadsided with a 50mph gust WILL push you off the track! Willow Springs in southern California. I thing that the biggest problem was the carb tuning as rides with our carburetion setups could: run with or without float bowl tubes, tuck their knee in of out, draft to the inside or outside of another rider while in a strong crosswind! It’s been a few years, but I definitely do remember the lack of problems with crosswinds. Urban myths started by someone in the States! Do the hoses affect the carburetion? Perhaps, to a very small effect. Less than running the bike again and increasing the crankcase temp 10F!

The only thing I can say is that we did a run with- and without the tubes installed and the effect was very clearly visible on the dyno graph. So when you fit separate K&N filters be sure to fit those hoses for the horses!

Before anything, I would like to have it said that I wrote this in my best knowledge and do
not want to be held responsible for any mistakes. I’m confident about what I’ve seen and done,
but since I’m not the only one messing around with gixxers, I can hardly ever be sure that
the engine I find in a 89 1100R is really an 89 1100R. I’ve left the types before 88 out,
since I have not much experience with them.

Frankenstein@robbynitroz.nl

There are mainly 2 types of 750’s, the 88-89 short stroke, and the pre-88 and 90-91 long stroke.
(The 750F is basicly the same motor as the 88-89 short stroke, the B6 and GSXF600 are basicly
the same as 90 long stroke with a smaller bore).
1100R motors from 88-92 are similar to the 1100F and B12 motors. The 1100G is also similar,
but has an axle drive. They all have the same stroke, and only the B12 has a 1mm bigger bore.

Apart from the color, all the GSXR, GSXF, GSXG and Bandit ignition covers are the same (except
the 750RK).

The clutch covers are depending on the clutch operation, there are 3 possibilities:
(The dry clutch is left out, to avoid making it more confusing).
1.The GSXF600, GSXF750 and B6 have the clutch cable connected to a mechanism on the sprocket
cover, and the clutch is operated by a push pin through the primary gear box shaft.
2.The 750R has the clutch mechanism in the clutch cover (on the right side). The 88-89 clutch
cover is recognizable by a smooth clutch cover, the 90-91 has a bubble in the center. They are
very similar, but since the engines have a different clutch, I don’t think these covers can be
swapped, I haven’t tried though.
3.The 1127’s and B12 all have the clutch mechanism on the sprocket cover, like the 600’s and
the 750F, but then hydraulically operated. The mechanisms on the sprocket cover can all be
swapped, so it’s possible to put a cable operation from a B6, F6 or F750 on an 1127 (and v.v.),
although it might need some adjustment of the length of the pushrod.
This also means that, since the clutch covers on the 600’s, 750F and 1127’s are nothing but
covers, they can be swapped.

The startermotor covers from the 1127’s are all the same (The startermotor covers from the 1052
engines are not the same) The 1127 covers can be recognized by a kind of bubble, to accomodate
the bigger starter motor. The 600′ and 750’s have a smaller starter motor, and the top line of
these covers is straight. (I believe the 1052 motors also have this smaller starter motor and
cover). Covers can be swapped among the 600’s and 750’s, but an 1127 cover only fits an 1127.

The oil pan on all 1127’s are the same, but the B12 is different. The 750F and 750R 88-89 have
the same oil pan as the 1127’s. The 91-750R and B6 have a similar or same oil pan as the B12,
I’m not sure. However, it is possible to swap these oil pans, as long is you change the oil
pickup as well. Oil hoses on the 1127 pans connect at the front, the others at the bottom.

The valve covers are different depending on the cam chain type, and the cylinder head size.
The B6 cover only fits the B6, the B12 cover only fits the B12. The 750R-90 and 91 covers
are the same. All the 1127 and the 750R-88/89 cam covers are the same.

There a 3 main items which make the difference in crankshafts.
1. Stroke
2. Clutch gear
3. Camchain type

1. The 1127’s and B12 all have the same stroke. The 600’s and 90-91 750R’s have the same
stroke. The 88-89 750’s and the 750F have the same stroke.
The stroke is important because this directly reflects on the number on teeth on the
clutch gear (ie. the gear diameter).
2. All GSXR1127 crankshafts are the same. The GSXF and G have a helical
cut gear, so when using a GSXF1127 crank You will have to use a GSXF1127 clutch basket as well.
3. All GSXR’s (both 750 and 1127) have the same type camchain, but the B6 and B12 are
different. Since the cam chain is driven from the crankshaft, this means these crankshafts
are not interchangeable with GSXR crankshafts, unless you also change the cam chain, tensioner,
guides, cam sprockets, cam covers, cam guiding between cam shafts.

All the 3 items above have to match. Swapping a crankshaft with a type that has the same
stroke, clutch gear and cam chain is no problem. If you start mixing, you have to match
clutch to the crankshaft (and in some cases gearbox), or cam chain stuff to the crankshaft.

Connecting rods from B6, 750R-90 and 750R-91 can be swapped. 1127 rods are all the same.
I have used B12 rods in 1127’s; I found there was a minor weight difference, but they could
easily be matched. This difference might have been incidental.

I left out the dry clutches on purpose, since I have no experience with them.

The GSXR1127 89-on and B12 have a diaphragm spring, the GSXF/G have normal springs.
The GSXR and B12 have a straight cut gear, the GSXF/G have a helical cut gear.
Because of the different gear on the clutch basket, the clutch basket is not swappable.
Since the types with a diaphragm spring have a longer shaft to accommodate the bolt for the
central spring, these parts are also not swappable. It is possible to use the internal clutch
parts from a ‘normal spring type’ in the basket (or actually on the gear box shaft) from a
‘diaphragm spring type’, but you need to fill the space on the longer shaft. It is not
possible to use the diaphragm style clutch on a GSXF gear box shaft, since the shaft is to short.

The 88-89 750R have a large (actually the largest) diameter but relatively flat clutch.
Although the gear box shaft is the same, the 88-89 clutch can not be swapped with the 91
clutch because the crankshaft diameter (and consequently tooth count) is different.
Although the B6 clutch is the same diameter as the 91 750R clutch (since they have the
same stroke), there is not a lot to swap there since the plates are different and the
gear box shaft are differently machined.

Cylinders block with pistons from 1127’s can all be swapped. B12 block+pistons fit the 1127
as well, or only pistons+have your 1127 block bored.
88-89 750’s is same as GSXF750.
B6 and 90/91 750R have 18mm wrist pins, whereas 88-89 750R, GSXF750, 1127’s and B12 have
20mm pins.
Since the B6 and later 750R 90-91 have the same stroke, cylinder block dimension, and wrist pin
diameter, the 90/91 block+pistons can be swapped with the B6 stuff (although you’ll have to
check that the pistons don’t hit the head/valves).

The long stroke engines (ie. B6, GSXF600, 90/91 750R) have the same dimensions, just the
combustion chamber and valves in the 750’s is bigger. So somebody who want less power could
fit a B6 top on a 90 750R. Camshaft type on the B6, GSXF600 and 90 750R is forked rocker,
meaning 1 cam for each pair of valves. 91 750R has shim type with 1 cam for each valve.
If swapping the camshafts as well, the 90 and 91 heads can be interchanged.
Both the 90 and 91 750R top ends can be used on a B6, but since the B6 has another type of
camchain, it is needed to maintain the B6 cam chain tensioner, guides, cam sprockets, valve
cover etc.

The 750 short stroke engines 88/89 heads have the same outside dimensions as the 1127/B12,
but the combustion chamber is smaller (although the valves are the same diameter).
The 1127R-91/92 has the same style head as the 750R-91, but
not much to swap; 1100 valve spacing differs (so camshafts can not be swapped), 1100 valves
are bigger, outside head dimensions differ.
As mentioned, 750R-88/89 valves are the same as 1127/B12, exception are the 1127R-91/92 valves.
These heads have shim type adjustment, and therefore different cams and longer valves.

It is possible to modify a 1127 shim head to a forked rocker head. It’s quite some work, and
you’ll need the valves from the forked rocker head, the rockers, cam shafts. You’ll need to
make all the spacers yourself, or in fact I believe there is a company that has or used to
have a modification kit.

Cam shafts from the 1127F, 750F, 90-750R, B6, B12, 88/89 750R are theoretically all swappable,
but of course the profiles are different. The long stroke 750’s have a different tooth count
on the cam sprockets so they can not be mixed. B12 sprockets can only be used in the B12.
B6 sprockets can only be used in the B6. 1127F and 1127R sprockets are the same, 88/89-750R
sprockets are similar, but the timing marks are different. (Meaning they can only be used if
slotted and timed)

1127: Depending on the clutch type there are long and short shafts. Also the gears themsleves
from these boxes are different. It may be possible to swap a few gears between these boxes,
but the gearchanges might not be very smooth.
Apart from the clutch type, the 91-92 1127R has a double row bearing on the output shaft, and
therefore a slightly different crankcase (around the bearing area).

Gear boxes from all 750’s are swapable. I have no experience with swapping gears seperately.

The B6 has a different shaft, so it can only be used with it’s own clutch.

Although it might seem there are so many differences, a lot can be mixed, as long as the right
parts are choosen, a few examples.
(There are some basic guidelines to assemble an engine, like check compression, cam timing, valve
clearance etc., no matter what combo you’re making).

1. A 1052 crank fits in 88-89 750R and 750F cases, but a 1127 crank doesn’t (but the cases can
be modified to take the 1127 crank as well)

2. A 750R-90 or 750R-91 top end on a B6.
It’s actually very easy, and I think all the info you need is above. Both engines have the same
stroke, same wrist pin diameter. Theoretically, it would be possible to put only 750 cylinders
and pistons on a B6. However, the pistons are designed to fit the 750 head and since that also
fits, why not install a 750 head as well (with bigger valves). Since the B6 has another cam chain
the B6 cam chain tensioner, cam sprockets, cam chain guides and B6 valve cover need to be
used. Then there are 2 options: either go for a 750R-90 top end, which uses forked rockers
like the B6 does (so it’s possible to use either the B6 cams or the 750R cams), or go for a
750R-91 top end, which uses another type of rockers so it is not possible to keep the B6 camshafts.

3. A 750R-88/89 top end on a 750R 90/91 bottom end (or 86-87 bottom).
This is a bit more difficult, since it needs some more work and imagination then the plain
assembling of a B6/750.
The 750R-88/89 have a bigger bore, so the idea of this combo is to increase the capacity of the
engine. (You could also take this combo the ‘other way around’, and fit a 90/91 crankshaft + clutch
in a 88/89 engine.)
Since the dimensions of the heads are not the same, it is not possible to only put the 88/89 pistons
+cylinders on the 90/91; the head of the 90/91 would not fit the cylinder block. So the complete
88/89 top has to be installed on the 90/91. The wrist pins on the 90/91 are 18mm, on the 88/89 20mm,
so the small end of the 90/91 rods have to be bored to 20mm. Now the whole thing could mechanically be
assembled, but since the stroke of the 88/89 is smaller, the height of the cylinder block is smaller.
This has to be compensated by putting a spacer under the cylinderblock. (This spacer would very
roughly have to be 1/2 x the difference in stroke, but the only right way is to measure/calculate the
compression.

4. 750R 6 box in a 1127 motor
The only hard thing here is to have a hole drilled through the gear box shaft, for the pushrod.
The 750 6 boxes have a single row bearing on the output shaft, and the clutch does
not have a diaphragm spring. So the easiest 1127 engines to put a 6 box in are the ones with a
single row bearing on the output shaft, and no diaphragm clutch, ie. only the GSXF1127 engines.
In these engines the 6 box drops straight in, only the shaft has to be drilled.
Second easy would be an 1127R engine with a diaphragm clutch, but no double row bearing (88-90).
In this case the box would still drop in, but for the clutch one would have to use the inner
clutch parts from a GSXF1127 (with normal springs) and the outer clutch basket from the 1127R
(with a straight cut gear, not helical).
Most work is in a 91/92 1127R where one would have to match the clutch as above + find a
solution for the double row bearing (the solution is actually to turn the double row bearing
inside out, and make a little hole for the small pin).
Of course the shift drum and forks from the 6 box have to be used as well, but they drop in
any 1127 without problems.

5. 88-89 750R head or 750F head on a 1127 or B12
These heads fit as they are, and give higher compression, better ports, larger squish.
In the case of the 91-92 1127R you’ll need to use the 750 camshafts as well, since the
91-92 1127R uses shim type camshafts and the 750 head is forked rocker type. If you use the
91-92 1127R cam shaft sprockets they can be timed as in the manual.
In the B12’s case you could use the B12 or the 750 cams (although they have different profiles)
but will have to use the B12 cam shaft sprockets because of the different cam chain.
In the case of the 88-90 1127R you can use the 750 or 1127 cams, and use the 1127 cam sprockets
(timing ‘by the book’) or use 750 cam sprockets (timing to be done by yourself)